fix: the current song play position and queue is preserved on app close

[bmcwilliams96]

Previously, the current queue and play position was discarded when the app closed. This PR addresses this and preserves the play position and current queue on app close so it can be applied when the app starts. This is a separate feature from the existing "Song Playback Resume" feature and will not affect/be affected by it.

[BLeeEZ]

Hi, I am sorry but I don't get this PR. What is the benefit of this feature? The current playing song is already saved in CoreData. The progress time in the song is also saved when activated with "Song Playback Resume".

[bmcwilliams96]

In my own experience with the app, whenever I close out of the app and come back, the play position of the song I was listening to usually gets reset, and my current queue is usually gone. This PR snapshots the state of the song and the queue so when I come back I can pick back up where I was. Unrelated to the "Song playback resume" setting, which just resumes your spot in a song if you come back to it another time, even if you listen to other songs in between. this isn't a viable solution for me since I sometimes skip a song halfway through, but don't want to pick back up on it next time it comes up on shuffle like a week later or something. I would rather it restart at that point :)